Intercommunicating telephone system



June 17, 1947. w. T. POWELL INTERCOMMUNICATING TELEPHONE SYSTEM Fi'led Aug 24, 1944 2 Sheets-Sheet 1 f 9 a MM 5 a a 1w 7 I a -4 5 r /m m 1.51m: .ll 7

i fi J FT k v i L @J M 8 T g 1| a 5 4 b i 3 H. U S l I l I l I I I I nm H. 0.l M A 7 a w m N m M vn M 0 T '4 N M 0 E V N N L n u a 5 \L m F on 0 m .r m m F m m 2 m M R M .L E E M m R M R l! F K W v M N r M w W 0 U T T T m I? (Ch? v JNVENTOR. Wl/VFRED r POWELL A TTORNEY Patented June 17, 1947 IN TERCOMMUN ICATING TELEPHONE SYSTEM Winfred T. Powell, Rochester, N. Y., assignor to Stromberg-Carlson Company, Rochester, N. Y., a corporation of New York Application August 24, 1944, Serial No. 551,004

This invention relates to a telephone system in which dial controlled relays effect intercommunication between a limited number of telephone subscribers or interconnection with one of several trunks leading to an exchange.

The various features and advantages of the invention will appear from the detailed description and claims when taken with the drawings in which:

Figs. 1 and 2, when arranged side by side in the order named, diagrammatically represent a telephone system incorporating the present invention. Fig. 1 at its upper and lower portions indicates two complete telephone line circuits together with the relays individual thereto, while in the intermediate portion of Fig. 1 other telephone lines are merely indicated. Fig. 2, on the other hand, shows control equipment common to the mentioned lines as well as two trunks leading to a distant exchange.

In this system, as herein illustrated, there are provided six telephone lines and two trunks leading to a central ofifice. There are provided six counting relays, five control relays and two trunk relays common to all of the lines as well as a line relay and two trunk relays individual to each telephone line when two trunks are used in the system. However, by the addition of another pair of counting relays, the number of lines in the system can be increased to eight. In the present arrangement only three wires extend to each substation where the telephone line is provided with a dial, a direct current bell and a push button. The push button is used to transfer to another telephone, a call incoming over a trunk to a given telephone. In this system, common dialing and talking circuits are used and therefore trunk selection cannot be made while a local connection is established. However, local calls are not secret, and consequently a party wanting a trunk connection, can break in on the local call and request the parties to the local call to hang up. In the present layout, no busy tone is required since only one party can dial at a time. If a party gets the common dialing circuit and hears no one else on this circuit, it is an indication that no local line is busy and any telephone of the group can be selected. In the case of trunk calls, the absence of dial tone from a dial control office indicates that the selected trunk is busy. In

Claims. (Cl. 179-47) the case of a connection with a manual central oilice, if a trunk call is not answered within a reasonable time, the local party hangs up and dials the other trunk number.

It is believed that the operation of this sys- 2 tem will best be understood by describing a telephone connection from the substation A on a telephone line it I!) to a substation B on the line having the designation #60. When the subscriber at A removes his receiver from its switchhook, it completes a circuit from the negative side of battery, winding of the common relay 5, back contacts and continuity springs of the switching relays 6 and i, winding of the slowreleasing line relay 8, ring conductor 9, through the substation circuits at A, tip conductor H3, back contacts and continuity springs of relays I and 6, conductor H, to the positive side of battery. Relay 5, on operating, closes an obvious operating circuit for the slow releasing relay'l2.

Since it has been assumed that the calling subscriber wishes to call the subscriber at substation B on the line which is designated #60, the subscriber at A operates his dial sender to transmit six impulses. In response to each of these impulses, the common relay 5 is released six times, after which it remains operated. While the line relay 8, which is slow releasing, may or may not respond to these impulses, this is immaterial since the line relay 8 performs no useful function at this time. On the release of the common relay 5 in response'to the first impulse of the series, the slow releasing change-over relay I3 is energized in a circuit completed at the front contact and armature of relay l2 and at the back contact and armature of the relay 5. The first release of the relay 5 also closes a circuit for operating the first counting relay [4 of the series. This circuit extends from the negative side of battery, winding of the relay l4, innermost back contactv and armature of the #2 counting relay l5, uppermost armatureand back contact of ringing relay II, conductor l6, armature l8 and back contact of relay 5, front contact and armature of relay l2 to the positive side of battery. Relay I4, on operating, locks itself in this condition, through its outer, upper armature and front contact,'front contact and armature of V relay I2, to ground. When the relay 5 operates again at the end of the first impulse, the #2 counting relay I5 is operated in a circuit traceable from the negative side of battery, winding of the relay l5, uppermost armature and front contact of relay 5. conductor 16, back contact and armature of relay l1, armature and front contact of the #I counting relay [4, conductor l9, front contact and armature of relay 12 to the positive side of battery. As soon as the #2 counting relay is operated, it closes a circuit for operating the #3 counting relay 20. This circuit extends from the negative side of battery, winding of relay 20, back contact and armature of the #4 countin relay 2!, front contact and armature 22 of the relay l5, conductors 23 and Hi to the positive side of battery at the armature and front contact of relay [2. When the relay releases at the beginning of the second impulse, the #l .countingrelay i4- releases and when the relay 5 operates at the end of the second impulse, the #2 counting relay I5 is released. This operation of the #l counting relay l4, and the #2 counting relay l5 follows the operation of the relay 5. In other words, the counting relay shifts its position at the beginning of each impulse repeated by the relay 5,

on releasing. Thus, the #l counting relay is operated at the beginning of each odd numbered impulse and released at the beginning of each even numbered impulse. The #2 counting're lay I5 is operated at the end of each odd mumbered impulse and is released at the end of each even numbered mpulse, as repeated by the. relay 5. The #3; counting relay 2!]: and the #4. counting relay 2! are operated in response to. the operations of the #2 counting relay E5 in the same manner as the #l and #2 counting relay were operated by the relay 5, otherwise expressed, the #3 counting relay 2i] shifts its position each time that the #2 counting. relay is operated. and the #4 counting relay 2 l. shifts. its position each time that the #2. counting relay is released. The #5 counting relay 24 and the #6 counting relay 25 are controlled by. the #4 counting relay 2|, in the same manner that the #3 counting relay and the #4 counting relay are governed by the #2 counting relay l5. From the foregoing, it shouldv be, understood that a counting relay circuit. arrangement is provided in which the number of channels that can be. selected is doubled by the provision of each additional pair of counting relays. I

Under the condition assumed in which the digit 6 was dialed to. select substation B, at the end of this series of impulses, the #l counting relay. ill, the. #2 counting relay I5 andgthev #5 counting relay. 2 3. will be in their released positions, whereasthe #3 counting relay 2B; the #4 counting relay 2!, and. the #6 counting relay 25willbe in their operated positions.

At the end of this series of impulses, the slow releasing, change-overrelay I3, and the slow releasing relay 2 lwi-llbe released in sequence, relay 2! having been operated by the closure of the lower outer front contact; of relay l3. The change-overrelay on releasing closes a circu-it for operating the'ringing relay ll fro-m th'e positive sideof battery, winding of this relay, front contact and armature of slow releasing relay 21, back contact and armature of changeover relay i3 and through the resistor, to the 7 negative side of battery. The ringing relay I1 is operated in this circuit and closes a locking circuit for itself through its lower front contact and armature, armature and frontcontact of relay l2, through the resistor, to the negative side of battery. Thus, the locking circuit of the ringing relay is maintained even when the slowreleasing relay 2! releases. The ringing relay, on operating, prevents additional dial impulses from changing the setting of the counting relays. v V

' It'now'becomes necessary to ring the bell at the substation B of" the wanted line. "In order to effect this ringing, the subscriber at substatiOn A operates his dial to transmit aseries of impulses which may be ten innumber if along ringing period is desired. These impulses effect the intermittent release of the relay 5 which relay efiects the operation of the slow releasing change-over relay is at the beginning of the series of impulses. When the relay 5 is again operated after the first impulse, th slow releasing relay 2? is operated from the positive side of battery, winding of this relay, front contact and armature of the ringing relay ll, front contact and armature of the change-over relay I3, lower front contact and armature of relay 5 to the negative side of battery. It will be noted that the relay 2? does not have its circuit completed unless relay 5. operates following its release in response to: the second digit.. This condition is to prevent th ringing of a called station when the. calling party hangs up and thereby releases the relay 5 without turning the dial to effect ringing operation. The circuit for ringing the call bell at substation B extends from the negative side of battery through the resistor, lower armature and front contact of relay l3, armature and front contact of relay ll, conductor 30 front contact and arr-nature of relay 21 and thence over the executing conductor 3|, armature and back contact of the #5 counting relay armature and front contact ofv the #3 counting relay 20, armature and back contact of the #i counting relay I4, conductor 32', back contacts and armatures of the switching relays 33 and fi l, which. relays 33 and 34 are the trunk relays for line #6, Xline conductor 35, back contact of the switch-hook at station E, armature and back contact 35 and winding of. the bell 31, tip conductor. 38, continuity springs and back contacts of relays. and 33, conductor 39., to the common ground connection. The completion of this circuit causes the intermittent operation of the bell 31- over the conductor 35 of the called line for a period of time determined by the number of impulses in the. ringing. digit and also the slow acting time of the change-over relay l3.

. When the called party answers, his. telephone circuit including the conductors 3.8. and 40 is connected in multiple with' the tip conductor l0 and the ring conductor 9 of the calling partys telephone circuit sothat the conversation may be carried on. When both the calling party and the called party hang up, the circuit including the relay 5 is opened for effecting the release of this relay. This in turn effects the release of the slow releasing relay l2. Relay l2- effects the releaseof the ringing relay H as well as any counting relays which have been left operated. It

4 will be noted that when the relay 5: releases and before the relay l2 releases, the change-over relay i-3- will be operated but this operation performs no useful function. It will also be seen that the line relay 4] is operated when the called party removes his receiver from its switch-hook but this operation likewise performs no useful function.

It has been mentioned that the present system provides means for connecting the telephone circuits to one or more trunk circuits leading to an exchange. As herein illustrated, two such trunks are provided, one of which is designated #l-i and can be selected by dialing dig-its corresponding to that-number and the other trunk is designated 81 and, can likewise be selected by dialing that number. For purposes of description, let it be assumed that it is desired to select the second trunk which is selected by dialing 81. Under the conditions assumed, the party at A removes his receiver from its switch-hook and switching relay 5 in an energized condition.

. 5 first dials the digit #8. In response to the impulses of this digit, the relay 5 vibrates its armature. This causes th operation of the slow releasing relay l2, change-over relay l3, relay 2! and the ringing relay H and the counting relays in the same manner as previously described for a local inter-station call. The counting relays are thus operated in the proper combination with all counting relays left de-energized to extend the execution conductor 3] to the #8 terminal, herein designated 42. Thereafter, when the subscriber at A dials the digit #1, relay 5 first releases and thenoperates again. The release of relay 5 closes a circuit for operating change-over relay [3 and at the same time that the relay 5 releases and operates, the line relay 8 of the calling line may release and may reoperate in like manner. 1 Execution now takes place by reason of a circuit now closed from battery through th resistor, front contacts and armatures of relays l3 and I7, lowermost armature and front contact of relay 27, execution conductor 3!, and through the armatures and back contacts of the counting relays i4, 26 and 23 to the #8 terminal, conductor 33, thence through the armature and back contact of relay 44, conductor 45, back contact, continuity spring and winding of the relay 6, back contact and armature of trunk switching relay 1, front contact and armature of the line relay 8 of the calling line to the other terminal of battery. The relay 6 operates and closes a locking circuit for itself from the positive terminal of battery, armature and front contact of relay 8, armature and back contact of relay '8,

winding of the relay 6, its continuity spring and armature, conductor 46, winding of the relay M, to the other terminal or battery. The operation of the relay 44 opens up the channel conductor, including the leads 43 and 45, for the purpose of making this trunk busy in the event that it is dialed by another station. The relay 6 switches the tip and ring line conductors, designated l0 and 9 to the conductors 48 and 49 of the trunk 8i. Switching relay 6 on operating, disconnects the calling line from the common dialing and talking circuit which effects the release of the relay 5 and the slow-releasing relay ii in sequence. The release of the relay 5 effects the release of the relay '2'! and the release of the relay l2 effects the release of relay l3 and the ringing relay I1, thereby restoring the common dialing and talking circuit to its normal condition so that it can be used by another line. It willbe understood that any other local call may now be established and another trunk call can be extended by dialing 71 in the event that that trunk is idle. In this way, trunks H and 8! may be used at the same time and also local interconnections may be established.

An incoming call over either of the trunks H or 8i signals by ringing the bell, such as 59 for trunk 8i, located within hearing distance of one of the stations. In the answering of this call, some one of the six stations of the system dials the associated trunk number, for example, #Bi which effects the circuit operation in the same manner as that described. If that line is the one designated M0, the line relay 8 of this line circuit remains operated for maintaining the It should be mentioned that the line relay 8 and the switching relay 5 are slow releasing so that the local station may signal a manual central station (not shown) or may dial into a dial cen tral office (likewise not shown) without releasing the connection, if the mentioned openings of the line circuit are of not too great duration.

This system also provides for transferrin a call. For example, if the incoming call just described is answered by the party on line circuit #16, when the party calling over the trunk, wishes to speak with a party on some one of the other line circuits .of the system, this transfer can be effected by the party answering the call, without releasing the trunk connection. Since this is a trunk call, the line relay 8, the switching relay 5 and the trunk channel relay 44 will be operated in the event that the trunk #8l is in use. The circuit closing device such as push button E-l at the station is now operated to cause the differentially connected relay 52 to operate. The circuit for the relay 52 extends from battery at the exchange, trunk conductors 53 and 358, armature and continuity spring of the switching relay 6, back contact and continuity spring of the relay l, winding of the line relay 8, line conductor 9, contacts of the push button now closed, hook switch contacts now closed, conductor 54, armature and back contact of switching relay l, armature and front contact of switching relay 6, conductor 55, lower winding of relay 52, tip conductor 56 of the trunk, to the other side of the battery at the central oiiice. Relay 52 on operation, locks itself operated through its lower winding and its inner armature and front contact'over the tip and ring conductors 56' and. E3 of the trunk #Bl. The mentioned inner front contact and armature of relay 52 also short-circuits the relay 8 of the line #59 to effect the release of the line relay 8 which in turn releases the switching relay 6 and the channel relay 64. After the switching relay 6 releases, the closed circuit of station #lil operates the line relay 8 and the relay 5. The relay 5 operates the slow releasing relay l2 and the calling line #lfl is now connected to the common dialing and talking circuit so that the wanted party can be selected and instructed to dial the trunk #Sl. Then after this trunk numher is dialed by the wanted station, such as #69,

and when this trunk is selected and when execution takes place, a circuit is completed from battery to the #8 terminal which extends through a back contact of relay 34, back contact, continuity spring and winding of relay 33, back contact of relay 34 and front contact of line relay ii of the calling line to the other side of battery. Belay M is again operated in series with th locking circuit of relay 33.

It will be recalled that during the transfer of the call on the trunk #8! from station #18, the trunk relay 52 was locked energized from one side of battery at the exchange, not shown, tip conductor 56 of the trunk, lower winding of the trunk relay 52, its inner front contact and armature, ring conductor 53 of the trunk to the other side of battery. As a result of the subscriber on line #51 dialing the trunk #2, the execution circuit including the conductors 3 and will be completed to energize the switching relay 6. As a result of the operation of this switching relay, the upper winding of relay 52 of the trunk,

-is energized in the opposite direction from the energization through the lower winding thereof in order to cause this relay to release. The energizing circuit through the upper winding of relay 52 may be traced from one side of battery (not shown) at the exchange, conductor 55, upper winding of the relay 52, lowermost armature and front contact of this relay, conductor 58, arma i'acazgsecv tune and front contact of relay 3%., continuity springand back contact of relay 34, conductor .38 through the contacts of the hook switch at station B, through the contacts of the impulse sender, through the substation circuit, back contact of the push button, conductor 46, winding of the line relay 4!, back contact and continuity spring of relay 3d, .front contact and armature of relay 33, conductors 59 and 53 to the other side of battery at the exchange. The release of relay 52 .removes the shunt from the trunk, which shunt included the lower winding of the relay 52. In the event that the subscriber at station B wishes to transfer this trunk-call again, it can be transferred. in the same manner as the original transfer was effected.

What I claim is:

1. In a telephone system, a plurality of telephone lines having their talking conductors permanently connected together in common, an impulse sending device provided on each telephone 7 line, a series of sequentially operated relays common to .said lines .and operated in various combinations responsive to the number of impulses transmitted by a given sending device, a ringing circuit completed to a wanted telephone line, said ringing circuit being completed for a period determined by said last-mentioned sending device together with certain of said relays.

2. In a telephone system, a plurality of telephone lines having their tip and ring conductors permanently connected in common, each telephone line being provided with a substation including an impulse sender, a group of relays common to said telephone lines, means including the impulse sender of a calling line fo selectively operating said relays in various combinations, each combination of relays being distinctive of a given one of said telephone lines, and a ringing circuit extended to the wanted substation by the selectively-operated relays, said ringing circuit being completed responsive to the operation of the impulse sender of the calling line as long as the operation thereof is continued.

3. In a telephone system, a plurality of telephone lines having their tip and ring conductors permanently connected in common, each telephone line having a line relay and being provided with a substation including an impulse sender, a trunk common to said lines, a trunk switching relaylindividual to each line for connecting its line to said trunk, a group of relays common to said telephone lines, means including the impulse sender of a calling line for selectively operating said relays in various combinations, each com-bination of relays being distinctive of a given one of said telephone lines, one of said combinations being distinctive of said trunk, a ringing circuit for each wanted line, said ringing circuit being controlled by the combination of relays distinctive of the wanted line, and an operating circuit for the trunk relay of the calling line, said operating circuit being completed by the line relay of the calling line and by that mentioned combination of relays distinctive of said trunk.

4. In a telephone system, a plurality of telephone lines having their tip and ring conductors permanently connected in common, each telephone line having a line relay and being provided with a substation including an impulse sender, a trunk common to said lines, a trunk switching relay' individual to each line for dislays common to said telephone lines, means including the impulse sender of a calling line for selectively operating said relays in various combinations, each combination of relays being distinctive of a given one of said telephone lines, one of said combinations being distinctive of said -trunk,a ringing circut for each wanted line, said ringing circuit being controlled by the combination of relays distinctive of the Wanted line, and an operating circuit for the trunk relay of the calling line, saidoperating circuit being completed by the line relay of the calling line and by that mentioned combination of relays which is distinctive of said trunk.

5. In a telephone system, a plurality of telephone lines having their tip and ring conductors permanently connected in common, each telephone line having a line relay serially connected therein and being provided with a substation including an impulse sender, a trunk common to said lines, a trunk switching relay individual to each line for'disconnecting its line from the other lines and for connecting its line to said trunk, a group of relays common to said telephone lines, means including the impulse sender of a calling line for selectively operating said relays in vari- :ous combinations, each combination of relays :being -.distinctive got a given one of said telephone :lines, one of said combinations being distinctive or said trunk, a ringing circuit for each wanted line, said ringing circuit being controlled by the combination of relays distinctive of the wanted line, and an operating circuit .for the trunk relay of the calling line said operating circuit being completed by the line relay of the calling line and by that mentioned combination of relays which is distinctive of said trunk.

B. In a telephone system, a plurality of telephone lines having their tip and ring conductors connected in :common, leach telephone line having-a line relay and .being provided with a substation including an impulse sender, a circuit c'losingdevice locatedlat each substation, a trunk common to said "lines, a differentially wound relay associate'd' with said trunk, :a trunk switching relay individual 1130 each line for connecting its :line to said trunk, aigroup of relays common to said telephone lines, means including the impulse sender of a calling line for selectively operating said relays in various combinations, each combination of relays being distinctive of a given one of said telephone lines, one of said combinations b'eing distinctive of said trunk, an operating circui't for the trunk relay of the calling .line, said operating circuit being completed by the line relay of the calling line and by that mentioned combination of relays which is distinctive of said "trunk, means including a circuit closing device at the substation of a line connected to said trunk for locking one Winding of the differentially wound relay across said trunk, and means including another telephone line connected to said trunk in the course of a call transfer thereto impulse sender associated with each'of said telephone line circuits, a group of relays associated with said impulse responsive circuit, means including the impulse senderof a calling line circuit for selectively operating said relays in various combinations, each combination being distinctive of a particular called telephone line circuit, and a ringing circuit extended by the selectively operated relays and including at least one of the conductors of said called telephone line circuit.

8. In a telephone system, a plurality of telephone line circuits having their tip and ring conductors normally connected to a common impulse responsive circuit, a substation including an impulse sender associated with each of said telephone line circuits, a group of relays associated with said impulse responsive circuit, means including the impulse sender of a calling line circuit for selectively operating said relays in various combinations, each combination being distinctive of a particular called telephone line circuit, a ringing circuit extended by the selectively operated relays and including at least one of the conductors of said called telephone line circuit, and means responsive to the removal of the receiver at said called telephone line circuit for disa'bling said ringing circuit.

9. In a telephone system, a plurality of telephone line circuits having their tip and ring conductors normally connected to a common impulse responsive circuit, a substation includin an impulse sender associated with each of said telephone line circuits, a group of relays associated with said impulse responsive circuit, means including the impulse sender of a calling line circuit for selectively operating said relays in various combinations, each combination being distinctive of a particular called telephone line circuit, a ringing circuit extended by the selectively operated relays and including at least one of the conductors of said called telephone line circuit, means responsive to the removal of the receiver at said called telephone line circuit for disabling said ringing circuit, and additional means for disconnecting said calling line circuit from said common impulse responsive circuit and for connecting this line circuit to an individual trunk circuit.

10. In a telephone system, a plurality of telephone line circuits having their tip and ring conductors normally connected to a common impulse responsive circuit, a substation including an impulse sender associated with each of said telephone line circuits, a group of relays associated with said impulse responsive circuit, means including the impulse sender of a calling line circuit for selectively operating said relays in various combinations, each combination being distinctive of a particular called telephone line circuit, a ringing circuit extended by the selectively operated relays and including at least one of the conductors of said called telephone line circuit, means responsive to the removal of the receiver at said called telephone line circuit for disabling said ringing circuit, additional means for disconnecting said calling line circuit from said common impulse responsive circuit and for connecting this line circuit to an individual trunk circuit, and holding means for holding said individual trunk circuit when said calling line circuit is disconnected from said individual trunk circuit whereby a connection set up to said trunk circuit is maintained to permit the transfer of said connection to another line circuit of said plurality of line circuits.

WINFRED T. POWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,100,523 Saunders et a1 Nov. 30, 1937 2,320,885 Powell June 1, 1943 2,325,151 Saunders July 27, 1943 

